Pipe still



May 25, 1937. D. R. JoHNsoN PIPE STILL Filed Feb. 17, 1932 RMQRDO .20

Iiivt,

kb. S5

A TTORNE Y.

Patented May 25, 1937 PIPE STILL D. Ronald lIohnson, Ponca City, Okla., assigner to Continental Oil Company, Ponca City, Okla., a corporation of Delaware Application February 17, 1932, Serial No. 593,494

4 Claims. (Cl. 196-110) UNi'rsosrres Fries My invention relates to a pipe still and more particularly to a pipe still for use in the processing and pyrolytic treatment of petroleum hydrocarbons.

In stills of this character, it is customary to Vhave a convection bank protected from the radiant heat generated in the furnace by a bridge Wall and a bank of tubes designed to utilize the radiant heat generated Within the combustion space. If the convection bank is subjected to a high temperature of radiant heat, the Violent heating of the oil in this bank results inits decomposition and the deposition of carbon. This is particularly true of the upper tubes in the con- ]5 vection bank. It has been found that a temperature of 140()o F. should not be exceeded in the entrant gases into the convection bank.

In order to prevent the critical temperature from being exceeded, a reduction of the furnace temperature by the use of an excess of air is sometimes resorted to. It is obvious that this ineicient method results in a considerable loss of heat. In the United States Letters Patent to Primrose, 1,568,182, a method is shown of obviating the diiculty by the use of a heat absorbing means above the convection bank.

One object of my invention is to provide a tube still construction which will preclude the overheating of the oil in the tubes of the convection bank and thus eliminate the necessity for the use of an excess of air or the employment of the absorbing means.

Another object of my invention is to provide a novel method of insuring the prevention of overheating in the convection bank by means of indirect heat exchange to temper the gases entering the convection bank.

Other objects of my invention will appear from the following specification.

The gure shows a diagrammatic sectional View of a pipe still construction embodying one mode of carrying out my invention.

In general, my invention contemplates the provision of a plurality of screen tubes interposed in the space between the top of the bridge wall and the top of the furnace to form a screen or grid through which the convection gases must pass before entering the convection bank. This screen will shield the refractory material above the convection bank from the direct radiant heat and thus prevent this section of the furnace from reecting radiant heat onto the top of the convection bank. The oil to be processed may be introduced through the screen tube bank or other material to be heated may be passed through the screen tube bank.

The number of rows of screen tubes is limited only by the draught conditions and the temperatures desired in the convection section. It is 5 obvious that if the screen tube bank be made too large, the hot convection gases will be reduced too much in temperature.

Inasmuch as the screen tube bank will occupy a position of high temperature, I propose to make l0 the screen tubes of material which will stand somewhat higher temperature requirements than those existing in the other tubes of the still.

More particularly referring now to the drawing, which forms part of the instant specical5 tion and which is to be read in conjunction therewith; the furnace walls I may be of any suitable construction having air inlet openings 2 and burners 3. The interior of the furnace is divided by a bridge Wall 4 which defines a com- 20 bustion space 5 in which is mounted a radiant heat tube bank composed of tubes 6 disposed around the sides and top of the combustion space and designed to receive the radiant heat generated Within the combustion space 5. The hot 25 gases of combustion pass over the top of the bridge Wall il and downwardly on the other side thereof through the convection tube bank l composed of convection tubes 8 and out through the ue connection 9. Between the top of the fur- 30 nace casing and the bridge wall 4, I position a bank of tubes I0 which I designate the screen tube bank. As pointed out above, this bank may be composed of a plurality of rows of tubes Il.

The hot gases of combustion will be tempered 35 by indirect heat exchange with the material passing through the screen tube bank Ii). At the same time the screen tube bank ID will intercept the radiant heat generated in combustion space 5 and prevent it from striking the top of fur- 40 nace casing above the convection tube bank l.

It will follow, therefore, that the danger of the overheating of the upper tubes in the convection tube bank I will be eliminated.

Oil to be processed is introduced through pipe 45 I2, through valve I3 and passes through screen tube bank ID. Inasmuch as the incoming oil is comparatively cold there Will be little danger of this oil forming carbon deposits. The cold oil also will maintain the tube Wall temperatures of 50 the screen tube bank Within safe limits and thus avoid excessive stress and strain in the tubes. After the oil being charged leaves the screen tube bank, it may be passed through the remainder of the pipe still in any desired manner. For ex- 55 ample, it may leave the screen tube bank I 0 through pipe I4 and pass through valve I5 into pipe I6, it being understood that valves Y I'I and I8 are closed. From pipe I6, the oil may pass through the lower convection bank and out through tube I9 through portion 20 of the radiation tube bank through cross connection 2|, through the remainder of the radiation tube bank, through line 22, through the upper portion of the convection tube bank and out through line 23.

If desired, the screen tubes may be used for heating any other product that may be desired. For example, the screen tubes may be used as a separate coil for reforming gasoline or other light hydrocarbon material at pressures ranging from 400 to 1500 pounds per square inch and at y temperatures of 750 to 1250 F. Even though partial cracking is obtained in the screen tubes under this condition, a high velocity of ow may be used to prevent deposition of carbonaceous material and injury to the -screen tubes due to high temperatures. When the screen tube bank is being used in this manner, valve I5 will be closed and valve I I will be opened and the oil to be processed in the pipe still will enter through valve I8 and pass directly into line I6 as will be obvious from the drawing.

Thus it is seen that I have accomplished the objects of my invention. I have provided a construction which will prevent the overheating of the upper tubes in the conv-ection bank. I have provided means for controlling the temperature of the convection gases entering the convection bank. I have provided a pipe still which will prevent the overheating of the tubesin the convec tion bank and have provided a design which will enable the tempering means to be used as a separate heating system for special stocks. It is to be understood, of course, that water may be passed through the screen tube bank for conversion into steam. Likewise the screen tube bank may be used as a steam superheater. screen tube bank is serving its other useful purposes, it will at all timesact as a grid or a screen to prevent the impinging and subsequent reection of the radiant heat.

It will be understood that certain features and sub-combinations are of utility and may be employed without reference to other features and sub-combinations. This is contemplated by and is'within the scope of my claims. It is further obvious that various changes may be made in details within the scope of my claims without departing from the spirit of my invention. It is, therefore, to be understood that my invention is not to be limited to the speciiic details shown and described.

Having thus described; my invention, what I claim is:

1. A tube still comprising in combination a setting divided into two sections by a bridge wall While the and partition tube bank in substantially the same plane as the bridge wall, means for burning fuel in one of said sections, means communicating with the other of said sections for withdrawing gases of combustion from said setting, a tube bank disposed in said fuel burning section adapted to be heated mainly by radiant heat, a tube bank disposed in the other of said sections adapted to be heated mainly by convection heat, means providing communication betweenA said tube banks whereby hydrocarbon oil to be treated may be passed through said convection heated bank and said radiant heated bank in series, and means for passing an extraneous cool medium through said partition tube bank.

2. A method of heating hydrocarbon oils including the steps of generating gases of combustion in acombustion zone and passing the products of combustion through a gas passage, heating a hydrocarbon oil rst by heat exchange with the hot products of combustion in the gas passage, then mainly by radiant heat in said combustion zone, and then mainly by convection heat in the gas passage, and reducing the temperature of the gases leaving the combustion zone and entering the gas passage by heat exchange ywith an extraneous cool medium, in a zone exposed to direct radiant heat from the combustion chamber.

3. A tube still comprising in combination a means for passing an extraneous cool medium throughsaid separate tube bank for reducing the temperature of the hot gases oi combustion leaving said combustion space and entering said' gas passage.

e. A tube still comprising in combination a setting formed with a combustion space and a gas passage, a tube bank adapted, to be heated mainly by convection heat disposed' in said gas passage, a tube bank adapted to be heated mainly by radiant heatdisposed in lsaid combustion space, means connecting said tube banks in series for passage of oil therethrough, a separate heat ab` sorbing element exposed to direct radiant heat from the combustion chamber, interposed between said combustion space and said gas passage, and means for passing an extraneous cool medium through said separate heat absorbing element for reducing thev temperature of the hot gases of combustion leaving said combustion space and entering said gas passage.l

13. RONALDl JOHNSON.' 

